1. Field of the Invention
The present invention relates to the field of machining and more particularly to modifications allowing to ensure the tool exchange of a machining machine-tool under the best conditions.
2. Discussion of the Background
Machine-tools which today ensure very high speed machining, reduce the amount of time spent both in machining and part transfer and thus the time the tool is in use. Very high speed machining thus defines new criteria or at least more restrictive criteria in the time allowed to exchange tools, loading or unloading on the spindle(s), as well as loading and unloading in the tool magazine.
In fact, the tool exchange device of a very high speed machining machine-tool must be able to ensure under the best conditions, the following functions:
unloading from the spindle of the tool just being used,
its storage in a storage device,
the engagement of the tool in a storage device,
the loading of the tool on the spindle.
Another criterion to be added to that of speed is the quantity of tools offered by the said storage device. It is classical to use a rotary storage device so as to present the device ensuring the engagement of the tool as fast as possible with a free housing to house the tool having just been used, and after, by rotation of the device, to present the tool to use in the next machining stage.
Even though such a device, called with turret, answers perfectly to the needs of a machine-tool using a limited number of tools, it is not adapted to the case when the machining stage of the piece to be machined by the machine-tool, requires the use of a large number of tools.
It is nevertheless possible to make a larger number of tools accessible by doubling the number of turret devices which requires two tool exchange devices or at least doubles the space needed.
Amongst the turret devices, the rotary storage device described in the French patent No 2 748 225 which comprises a multiplicity of tools arranged on its periphery is known in the prior art. During tool exchange, the turret enters by rotation in the machining zone, a ram carrying a mobile electric spindle on three axes puts the tool having been used in the previous machining stage in an empty housing of the turret and takes, after a suitable rotation of the turret, the tool which is needed in the next machining stage.
The limitations of a turret device are as follows:
the number of tools is very limited,
the rotary movements of a turret carrying a large number of tools should be ensured by an oversized motorisation,
the turret should be of a very large diameter,
the doubling of turrets is not enough to supply enough tools for some applications,
the loading and unloading of tools during the function of machining is not possible,
the ram waits for the rotation of the turret before it can take the tool needed to be used in the following machining stage.
In the prior art there also exists a device in which the tool housings are integral with one another as well as with a driving means, thus constituting a chain moving to present, at the level of the exchange zone between the storage device and the machining station, either the empty housing to retrieve a tool having been used, or a housing containing the tool to be used in the next machining stage. It is obvious that the number of tools can be very large for such a storage device. Nevertheless, this same number of tools also determines the speed to go from one tool housing to another. Consequently, the more tools there are, the slower the speed to ensure storage of the tool having been used and to bring to hand the tool to be used.
The research of the applicant have therefore been oriented towards a high capacity tool storage and tool exchange device respecting the speed criteria defined by very high speed machining.
The inconvenience of increasing the number of tools, in relation to a classical device of a classical tool exchange, is that it increases the amount of time needed to unload the tool as well as to bring it towards the exchange zone between the tool storage and tool exchange device and the ram, due to the fact of increasing the travelling distance. The applicant has thus carried out research to also reduce the time of the functions mentioned above, research which has led to the original conception of a particularly new and inventive high capacity tool storage and tool exchange device obviating the inconveniences mentioned above and offering optimised tool storage and tool exchange functions.
According to the main characteristic, the tool storage and tool exchange device of a high speed machining machine-tool comprising a horizontal ram receiving a tool on its end, is remarkable in that it is made of the following parts:
a tool storage module comprising, inside a sealed chamber, a multiplicity of aligned housings receiving the tools so that the axes of those tools are parallel with the axis of the ram and form part of a same vertical storage plane,
a handling module which, moving in a vertical plane parallel with the tool storage vertical plane, ensures loading or unloading of at least one housed tool and its transport in the aforesaid chamber, along a direction parallel with the axis of the ram, from its housing towards an exchange zone with a third module and vice-versa, and
a transfer module ensuring transport of the tool present in the ram from an exchange zone with the ram towards the exchange zone with the handling module to transmit the tool to it, and vice-versa.
This characteristic is particularly advantageous in that it adds an intermediary module in the movement of the tool from its storage zone to its zone of use. In fact, it is not the transfer module which ensures the loading or unloading of the tool in the storage module, but the handling module. Inversely, it is not the handling module which ensures passage of the tool from the storage zone to the ram, but the transfer module.
So, by adding an intermediary element, it is parfectly possible to realise most classical functions of a tool storage and tool exchange device at the same time.
So, for example, the transfer module of the tools ensures the removal of the tool carried by the ram and its replacement by another tool while the handling module places another tool in the storage magazine. Alternatively, while the transfer module is ensuring the replacement of a tool, the handling module can get a new tool from the magazine.
The addition of an intermediary module therefore allows to carry on and not stop the machining when the handling module unloads a tool having been used and/or finds another tool. Consequently, the size, volume or capacity in tools of the tool storage module conceived by the applicant, does not affect the speed of tool exchange of the device of the invention, as the route to unload, load and transport from the exchange zone, between the transfer module and the handling module, towards the tool storage module and vice-versa, is taken on by a module independant of the one which ensures transfer.
This disposition demarcates itself from the prior art devices which, as in the case of a turret, oblige machining to stop when the tool storage device is rotating to present a housing to take the tool which has just been used and another housing containing the tool to be used in the new machining stage.
Contrary to the storage devices of the prior art which had a tendency to group together all the functions in the one and same device, this new tool storage and tool exchange device concept is particularly inventive in that it separates the principal functions of such devices in three modules so that these modules can each function independently.
In addition, the arrangement in which the axes of tools arranged parallel to the axes of the ram, (the tools being oriented in the direction of the machining) garantees a minimum of additional movement during the transport and the tool exchange. This arrangement is particularly advantageous in that the change of direction of a tool for transport means can require some significant speed increases. Consequently, the change of direction of the tool, as for example, in going from a position perpendicular to the axis of the tool carrier ram to a parallel position, can lead to a change in the efforts necessary for gripping and thus require means to grip and to move oversized tools.
The disposition of the tools according to which their axes are all parallel and included in a same vertical plane parallel to axis of the ram, has for advantage, apart from the fact that it avoids additional movements while moving, that it minimizes the width requirement of the combined machine-toolxe2x80x94tool magazine.
To complete the addition of an intermediary in the transport and tool exchange line of the machine-tool, from the ram to the tool magazine and vice-versa, the applicant has judiciously conceived the said handling module comprises two arms which are each fitted at their ends with a tool gripping mechanism, and which are arranged one on top of the other in a same vertical plane perpendicular to the aforesaid vertical plane of the tool storage. These arms take two positions, i.e.:
a first extended position of loading and unloading tools when the gripping mechanism becomes in line with the axis of the cradle,
a second folded position of tool transport when the gripping mechanism moves away from the vertical plane of storage.
This disposition enables to move two tools at the same time or at least to keep one gripping mechanism free from the engagement of a tool presented by the transfer module.
In combination with the doubling of gripping mechanisms of the handling module, the applicant has conceived a transfer module with two gripping means. This disposition where the transfer module has two gripping means has not only the advantage of being able to ensure the gripping of the tool having just been used and to present by way of a second gripping means the tool to be used in the next machining stage in the same movement of the transfer module coming in its exchange zone towards the ram, but also to allow limiting the duration of tool exchanges between the two transfer and handling modules.
Limiting the duration of the exchange between the different modules reduces the number of operations despite adding an intermediary element. Thus, the storage device of the invention comprising the following three modules,
a storage module,
a handling module and,
a tool transfer module,
the said handling and transfer modules being each fitted with two gripping means is remarkable in that it satisfies both the criteria for the capacity relating to the number of tools and also to the speed of loading and unloading the tools.
This device which provides optimal satisfaction in relation to the new criteria created by high speed machining, leads to, in view of its new and inventive conception, a particularly new and inventive operating process of which the different stages will be defined in the following description.
Although, the fundamental concepts of the invention have just been detailed hereinabove in their most elementary form, more details and characteristics of the invention will come out more clearly when reading the description hereinafter using, as a non limitative example and having regard to the attached drawings, an embodiment of a tool storage and tool exchange device according to the invention.